Fluid-powered linear actuators are well known. While providing a relatively high linear output force, in some situations it is desirable to significantly increase the output force. Moreover, in certain situations the linear output member needs a short and accurate, but yet high power stroke. Sometimes it is desirable to also provide the linear output member with a limited rotational output.
Whenever using a reciprocating piston drive arrangement, as the piston reciprocally moves from one axial direction to the other in response to application of fluid pressure to the piston head, backlash results from the slack existing between the power-transmitting drive parts. While accurate machining will reduce the backlash problem, this procedure substantially increases the manufacturing cost. Even with accurate machining, conventional machining techniques are virtually incapable of totally eliminating the slack which produces the backlash problem. Furthermore, to the extent more accurate tolerances produce actuator parts which fit tightly together and reduce slack, assembly of the actuator becomes difficult. While accurate machining reduces slack initially, should the power-transmitting parts wear during usage or otherwise lose their original tolerances, no means exist for elimination of the slack that develops without disassembly of the actuator and possible remachining or replacement of the parts.
It will therefore be appreciated that there has been a significant need for a fluid-powered linear actuator having an exceptionally high power, short and accurate stroke linear output. Certain embodiments of the actuator should provide a limited degree of rotational output. Moreover, the actuator should not require exceptionally accurate machining of the power-transmitting parts to eliminate slack that produces backlash. The actuator should be easy to assemble and provide means for substantially complete elimination of the slack causing the backlash problem after the actuator is assembled. Elimination of the slack should be accomplished in a simple manner without requiring disassembly of the power-transmitting parts from the body. Furthermore, the means for elimination of the slack should, with one adjustment, simultaneously remove the slack existing between all of the power-transmitting parts within the body. The present invention fulfills this need and further provides other related advantages.